Software as a service - software updates

I am currently performing vendor assessments on SaaS (Software as a service) remote EDC system, for use within a early phase CTIMP environment (UK).

One thing that keeps re - occurring during my assessment is the validation of SaaS systems and the implications on computer systems validation (Changes post system provision from the vendor).

Discussions with vendors, seems to elude to the fact that the systems can be updated without notification, updates cannot be paused or halted during the duration of a project, also meaning potential for testing mid trial, for updates not pertaining to the actual data of the project.

Has any one had experience of performing validation testing on updated versions of EDCs during a project ? Has anyone had any issues with updates being performed ?

Can any provide practice solutions or management/mitigating strategies for managing software updates, and patches for a SaaS ?

I've had experience of something similar (for software managing environment monitoring). I ensured that the software service provider gave me enough heads up about any patches and what they were that we could validate the patches ahead of time in the live environment. This was mitigated by that fact that environment monitoring could, in this case, be conducted manually so it wasn't unmitigated if something were to go awry. But, if you have a testing environment that you can test patches before they go live or have enough heads-up to evaluate changes then you are managing the issue. Fostering a good relationship with the vendor is key (although not always possible).